In recent years, a phase change memory using a chalcogenide material for a recording material has actively been researched. In a memory structure of the phase change memory, the recording material is interposed between metal electrodes. The phase change memory is a variable resistance memory that stores information by using a fact that the recording material between the electrodes has different resistive states.
PTL 1 (JP-A-2004-272975) discloses a memory using a variable resistance element in which a plurality of memory cells each having the variable resistance element changed in resistivity by voltage application is connected in series to form a memory cell series portion, and a select transistor is disposed on at least one end of the memory cell series portion.
Also, PTL 2 (JP-A-2005-260014) discloses the phase change memory in which memory blocks having the memory cells each including the memory element whose resistivity is changed according to a temperature are stacked together to realize an integration nonvolatile memory.
The phase change memory stores information with the use of a fact that a resistivity of the phase change material such as Ge2, Sb2, or Te5 is different between an amorphous state and a crystal state. The phase change material is high in resistance in the amorphous state, and low in the resistance in the crystal state. Accordingly, read of information is conducted by giving a voltage difference to both ends of the phase change memory, measuring a current flowing in the element, and discriminating whether the element is in a high resistance state, or in a low resistance state.
In the phase change memory, an electric resistance of the phase change film is changed into a different state by a Joule heat generated by a current for programming. Reset operation, that is, the operation of changing the phase change material into the amorphous state of the high resistance is conducted by rapidly decreasing the current and rapidly cooling the phase change material after a large current has been allowed to flow in a short time to fuse the phase change material. On the other hand, set operation, that is, the operation of changing the phase change material into the crystal state of the low resistance is conducted by allowing a sufficient current to keep a crystallization temperature of the phase change material to flow for a long time. The phase change memory suits for miniaturization in principle because a current necessary to change the state of the phase change film becomes small as the miniaturization is advanced, and actively researched at present.
As a method of integrating the memory using those variable resistance element, PTL 3 (JP-A-2008-16004) discloses that a plurality of through-holes that penetrates through a stacked structure in which gate electrode material and insulator films are alternately stacked in plural number together is formed by simultaneous processing, and thereafter a gate insulator film, a channel layer, and a phase change film are formed on inner walls of the through-holes to form the plurality of memory cells.
Also, as disclosed in NPL 1, a memory manufacturing technique using a method of forming the plurality of through-holes that penetrates through the stacked structure in which the gate electrode material and the insulator films are alternately stacked in plural number together by simultaneous processing is published in the phase change memory as well as a flash memory.